Phase I study of paclitaxel and epirubicin in patients with metastatic breast cancer: a preliminary report on safety.

Attempting to develop a new active, convenient regimen, we initiated a phase I study of paclitaxel (Taxol; Bristol-Myers squibb Company, Princeton, NJ) combined with epirubicin (Farmitalia Carlo Erba, Milan, Italy) in patients with metastatic breast cancer. In addition to standard eligibility criteria, patients with chemotherapy-naive metastasis and at least one measurable lesion had to have left ventricular ejection fractions of at least 50%; the metastatic relapse had to have occurred more than 6 months after adjuvant treatment. Anthracycline-pretreated patients could not have received cumulative doses of more than 300 mg/m2 doxorubicin, 450 mg/m2 epirubicin, or 70 mg/m2 mitoxantrone. An intravenous bolus dose of epirubicin was followed by a 3-hour paclitaxel infusion, with courses repeated every 3 weeks. To date, seven dose levels have been investigated and 31 patients have been treated, 19 of whom had already received anthracyclines. Grades 3 and 4 neutropenia occurred in 37% and 19% of 123 courses, respectively, with five episodes of febrile neutropenia. Grade 2 or 3 neurotoxicity has been observed in 42% of patients and cardiac toxicity in four patients (13%), all of whom had already received anthracyclines. One patient experienced transient myocardial ischemia, one had an asymptomatic decrease in ejection fraction, and two patients had clinical heart failure that required treatment. Dose-limiting toxicity was reached at dose level 5 (paclitaxel 200 mg/m2 plus epirubicin 60 mg/m2), with two of three patients experiencing febrile neutropenia. Reducing the epirubicin dose to 50 mg/m2, however, allowed the paclitaxel dose to be escalated to 250 mg/m2. At this dose level, only one of six patients experienced febrile neutropenia. At a preliminary response evaluation (dose levels 1 to 6), 11 patients (44%) had partial responses, 12 patients (48%) had stable disease, and disease progressed in two patients. We conclude that the combination paclitaxel/epirubicin is safe for patients with metastatic breast cancer and, at this early evaluation, shows promising antitumor activity. Additional patients will be treated at dose level 5 to confirm whether dose-limiting toxicity occurs at this step. Indeed, we took into consideration that dose-limiting toxicity observed at this particular dose level in two of three patients might be due to hazard, since paclitaxel dose escalation up to 250 mg/m2 was further possible in association with 50 mg/m2 epirubicin.